Proteins, such as keratin proteins, are beneficial in healing damaged epithelial tissues. Unfortunately, the chemical and engineering properties of keratin proteins have been relatively limited to those achieved using oxidative and reductive chemistries, and side chain protein crosslinks. A need exists for proteins, and methods for crosslinking proteins, preferably α-keratins, to form films having a broad scope of chemical and engineering properties so that the potential applications of protein-based materials can be expanded.